Anyone know what voltage the NiMh battery for the DX8 should be charged to? I received the charging cable from RC-Connectors and I am charging the battery outside the transmitter on my Thunder Power charger. Charging at 200 ma like the internal charger does but don't know if my Thunder Power will shut off automatically when it reaches full charge or if I should watch for a particular voltage. I know the battery pack says 4.8 V but that's not full charge. After about 1 hour it is still charging at 200ma and is up to 5.8V.

I cycled my stock pack 4 times with my Passport Ultra Charger. I charged and discharged at .5 ampere which is 1/4C. It takes about 8 hours for a complete charge/discharge cycle. After I did this intial battery "Conditioning". I just charge when it is needed while I am charging my Lipos. I usually never exceed 4 hours. I try to keep the voltage between 5.6 and 4.6.

Anyone know what voltage the NiMh battery for the DX8 should be charged to? I received the charging cable from RC-Connectors and I am charging the battery outside the transmitter on my Thunder Power charger. Charging at 200 ma like the internal charger does but don't know if my Thunder Power will shut off automatically when it reaches full charge or if I should watch for a particular voltage. I know the battery pack says 4.8 V but that's not full charge. After about 1 hour it is still charging at 200ma and is up to 5.8V.

Some peak chargers will have a tough time detecting peak at the low current you are charging at. I've found 1/4C(500ma) - 1/3C(660 ma) to be the minimum for my chargers to detect peak.

If the pack is warm...stop charging. If you have a temp probe for your charger use it to stop charge.

Battery was not completely run down, still showed about 5.2V on the transmitter. I put it on my Thunder Power at 200ma which is 1/10C and the charger shut off automatically after close to 2 hours and showing 5.83V. I guess I answered my own questions as the charger shut off automatically, the voltage hovered between 5.84 and 5.83 volts during the last hour of the charge so that must be the peak voltage. I purchased a LiPo and I plan on using that as my primary battery for the transmitter but will keep the NiMh charged up as a spare. I bought the Gforce 2700ma LiPo and plan to charge it on my external charger as well.

Honestly there is no need for any of this extra charging /discharging - jut do initial charge of 12 hrs .

I wish it was true, but I had a new one in my hands recently, fresh out the box and put it on charge as per instructions, but had to take it off charge a long way short of 12 hours as the pack was getting hot, not just warm but hot.

If I'd let it go to the full 12 hours that would probably have been a damaged pack straight out the box on the first charge.

Some peak chargers will have a tough time detecting peak at the low current you are charging at. I've found 1/4C(500ma) - 1/3C(660 ma) to be the minimum for my chargers to detect peak.

If the pack is warm...stop charging. If you have a temp probe for your charger use it to stop charge.

Don't depend on a peak charger functioning correctly at rates below 1/2C. It may or may not work, it's iffy. The type and condition of the cells, their state of charge and temperature all come in to play. The temp probe included with general purpose peak chargers is a fail-safe. Using it is a good idea, it terminates the charge cycle if the charger fails to detect a voltage peak.

1/2C is a good safe charge rate. 1/2C will not generate heat until the last few (5 to 10) minutes of a peak charge cycle. For example, 2000mAh NiMH (stock DX8 or Eneloop replacements) shouldn't warm, at all, during the first 90% of charging time charged at 1000mA (1 amp). At the very end of the charge cycle, they will warm up, just before a peak charger stops charging them.

A discharged NiMH pack charged at 1/2C should recharge in about two hours.

It should never become too warm to touch while charging.

Quote:

Originally Posted by jobog

Battery was not completely run down, still showed about 5.2V on the transmitter. I put it on my Thunder Power at 200ma which is 1/10C and the charger shut off automatically after close to 2 hours and showing 5.83V. I guess I answered my own questions as the charger shut off automatically, the voltage hovered between 5.84 and 5.83 volts during the last hour of the charge so that must be the peak voltage.

5.8V is a sane final voltage. The peak voltage charging at 1/2C is slightly higher, but it doesn't spend much time at that voltage. After the charge cycle completes voltage drops off quickly over a few hours, before leveling out between 5.6 and 5.4V. Eneloop cells retain their charge for many months. The cells used in stock DX8 packs self-discharge fairly rapidly compared to Eneloops.

Quote:

Originally Posted by Telrin

I wish it was true, but I had a new one in my hands recently, fresh out the box and put it on charge as per instructions, but had to take it off charge a long way short of 12 hours as the pack was getting hot, not just warm but hot.

If I'd let it go to the full 12 hours that would probably have been a damaged pack straight out the box on the first charge.

The charger built-in to the DX8 depends on the user monitoring the charge process. It's easy, remove the battery access cover and touch them. If they feel warm they're done. I tilt them out from the foam to improve cooling and aid in detecting the warmth that indicates they've finished charging.

If I'd let it go to the full 12 hours that would probably have been a damaged pack straight out the box on the first charge.

This is the primary problem with the DX8 charging. A user can follow the manual's charging recommendations precisely and it can still result in cooking the NiMH pack. Furthermore, the .3v offset may lead users to believe that their pack has not been fully charged leading to additional damaging charging.

Quote:

Originally Posted by LizardMan

Don't depend on a peak charger functioning correctly at rates below 1/2C. It may or may not work, it's iffy.

1/2C is a good safe charge rate. 1/2C will not generate heat until the last few (5 to 10) minutes of a peak charge cycle. For example, 2000mAh NiMH (stock DX8 or Eneloop replacements) shouldn't warm, at all, during the first 90% of charging time charged at 1000mA (1 amp). At the very end of the charge cycle, they will warm up, just before a peak charger stops charging them.

+1

Quote:

Originally Posted by LizardMan

It should never become too warm to touch while charging.

This bears repeating.

Quote:

Originally Posted by LizardMan

The cells used in stock DX8 packs self-discharge fairly rapidly compared to Eneloops.

My experience with the stock cells has been quite different. The cells in my tx have maintained their charge so well that I even suspected that they were LSD cells.

Quote:

Originally Posted by LizardMan

The charger built-in to the DX8 depends on the user monitoring the charge process. It's easy, remove the battery access cover and touch them. If they feel warm they're done. I tilt them out from the foam to improve cooling and aid in detecting the warmth that indicates they've finished charging.

Once the user is aware of the "special attention" required for DX8 NiMH charging, it is easy (albeit an inconvenience), but none of these precautions are mentioned in the manual. I don't do a full 10 hour (timed) charge until the battery hits 4.3v. If the battery is on the low side and I want to make sure I have enough power for a flying session, I just charge it for a couple of hours (2h charge ≈ 3h run time)

The charger built-in to the DX8 depends on the user monitoring the charge process. It's easy, remove the battery access cover and touch them. If they feel warm they're done. I tilt them out from the foam to improve cooling and aid in detecting the warmth that indicates they've finished charging.

Yes, I'm aware of this which is why I was checking it and why I avoided cooking it.

My comment was in reply to oft quoted, but inaccurate, advice that you can do a 12 hour first charge in safety.

Lol, well I thought I had a choice between audible and/or vibe for the inactivity alarm, not to disable it. Apparently I got confused with the choice for the other alarms and thought there was an option for the inactivity one.